fc(1p) — Linux manual page


FC(1P)                  POSIX Programmer's Manual                 FC(1P)

PROLOG         top

       This manual page is part of the POSIX Programmer's Manual.  The
       Linux implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior),
       or the interface may not be implemented on Linux.

NAME         top

       fc — process the command history list

SYNOPSIS         top

       fc [-r] [-e editor] [first [last]]

       fc -l [-nr] [first [last]]

       fc -s [old=new] [first]

DESCRIPTION         top

       The fc utility shall list, or shall edit and re-execute, commands
       previously entered to an interactive sh.

       The command history list shall reference commands by number. The
       first number in the list is selected arbitrarily. The
       relationship of a number to its command shall not change except
       when the user logs in and no other process is accessing the list,
       at which time the system may reset the numbering to start the
       oldest retained command at another number (usually 1). When the
       number reaches an implementation-defined upper limit, which shall
       be no smaller than the value in HISTSIZE or 32767 (whichever is
       greater), the shell may wrap the numbers, starting the next
       command with a lower number (usually 1). However, despite this
       optional wrapping of numbers, fc shall maintain the time-ordering
       sequence of the commands. For example, if four commands in
       sequence are given the numbers 32766, 32767, 1 (wrapped), and 2
       as they are executed, command 32767 is considered the command
       previous to 1, even though its number is higher.

       When commands are edited (when the -l option is not specified),
       the resulting lines shall be entered at the end of the history
       list and then re-executed by sh.  The fc command that caused the
       editing shall not be entered into the history list. If the editor
       returns a non-zero exit status, this shall suppress the entry
       into the history list and the command re-execution.  Any command
       line variable assignments or redirection operators used with fc
       shall affect both the fc command itself as well as the command
       that results; for example:

           fc -s -- -1 2>/dev/null

       reinvokes the previous command, suppressing standard error for
       both fc and the previous command.

OPTIONS         top

       The fc utility shall conform to the Base Definitions volume of
       POSIX.1‐2017, Section 12.2, Utility Syntax Guidelines.

       The following options shall be supported:

       -e editor Use the editor named by editor to edit the commands.
                 The editor string is a utility name, subject to search
                 via the PATH variable (see the Base Definitions volume
                 of POSIX.1‐2017, Chapter 8, Environment Variables).
                 The value in the FCEDIT variable shall be used as a
                 default when -e is not specified. If FCEDIT is null or
                 unset, ed shall be used as the editor.

       -l        (The letter ell.) List the commands rather than
                 invoking an editor on them. The commands shall be
                 written in the sequence indicated by the first and last
                 operands, as affected by -r, with each command preceded
                 by the command number.

       -n        Suppress command numbers when listing with -l.

       -r        Reverse the order of the commands listed (with -l) or
                 edited (with neither -l nor -s).

       -s        Re-execute the command without invoking an editor.

OPERANDS         top

       The following operands shall be supported:

       first, last
                 Select the commands to list or edit. The number of
                 previous commands that can be accessed shall be
                 determined by the value of the HISTSIZE variable. The
                 value of first or last or both shall be one of the

                 [+]number A positive number representing a command
                           number; command numbers can be displayed with
                           the -l option.

                 -number   A negative decimal number representing the
                           command that was executed number of commands
                           previously. For example, -1 is the
                           immediately previous command.

                 string    A string indicating the most recently entered
                           command that begins with that string. If the
                           old=new operand is not also specified with
                           -s, the string form of the first operand
                           cannot contain an embedded <equals-sign>.

                 When the synopsis form with -s is used:

                  *  If first is omitted, the previous command shall be

                 For the synopsis forms without -s:

                  *  If last is omitted, last shall default to the
                     previous command when -l is specified; otherwise,
                     it shall default to first.

                  *  If first and last are both omitted, the previous 16
                     commands shall be listed or the previous single
                     command shall be edited (based on the -l option).

                  *  If first and last are both present, all of the
                     commands from first to last shall be edited
                     (without -l) or listed (with -l).  Editing multiple
                     commands shall be accomplished by presenting to the
                     editor all of the commands at one time, each
                     command starting on a new line. If first represents
                     a newer command than last, the commands shall be
                     listed or edited in reverse sequence, equivalent to
                     using -r.  For example, the following commands on
                     the first line are equivalent to the corresponding
                     commands on the second:

                         fc -r 10 20    fc    30 40
                         fc    20 10    fc -r 40 30

                  *  When a range of commands is used, it shall not be
                     an error to specify first or last values that are
                     not in the history list; fc shall substitute the
                     value representing the oldest or newest command in
                     the list, as appropriate. For example, if there are
                     only ten commands in the history list, numbered 1
                     to 10:

                         fc -l
                         fc 1 99

                     shall list and edit, respectively, all ten

       old=new   Replace the first occurrence of string old in the
                 commands to be re-executed by the string new.

STDIN         top

       Not used.

INPUT FILES         top



       The following environment variables shall affect the execution of

       FCEDIT    This variable, when expanded by the shell, shall
                 determine the default value for the -e editor option's
                 editor option-argument. If FCEDIT is null or unset, ed
                 shall be used as the editor.

       HISTFILE  Determine a pathname naming a command history file. If
                 the HISTFILE variable is not set, the shell may attempt
                 to access or create a file .sh_history in the directory
                 referred to by the HOME environment variable. If the
                 shell cannot obtain both read and write access to, or
                 create, the history file, it shall use an unspecified
                 mechanism that allows the history to operate properly.
                 (References to history ``file'' in this section shall
                 be understood to mean this unspecified mechanism in
                 such cases.) An implementation may choose to access
                 this variable only when initializing the history file;
                 this initialization shall occur when fc or sh first
                 attempt to retrieve entries from, or add entries to,
                 the file, as the result of commands issued by the user,
                 the file named by the ENV variable, or implementation-
                 defined system start-up files. In some historical
                 shells, the history file is initialized just after the
                 ENV file has been processed. Therefore, it is
                 implementation-defined whether changes made to HISTFILE
                 after the history file has been initialized are
                 effective.  Implementations may choose to disable the
                 history list mechanism for users with appropriate
                 privileges who do not set HISTFILE; the specific
                 circumstances under which this occurs are
                 implementation-defined. If more than one instance of
                 the shell is using the same history file, it is
                 unspecified how updates to the history file from those
                 shells interact. As entries are deleted from the
                 history file, they shall be deleted oldest first. It is
                 unspecified when history file entries are physically
                 removed from the history file.

       HISTSIZE  Determine a decimal number representing the limit to
                 the number of previous commands that are accessible. If
                 this variable is unset, an unspecified default greater
                 than or equal to 128 shall be used. The maximum number
                 of commands in the history list is unspecified, but
                 shall be at least 128. An implementation may choose to
                 access this variable only when initializing the history
                 file, as described under HISTFILE.  Therefore, it is
                 unspecified whether changes made to HISTSIZE after the
                 history file has been initialized are effective.

       LANG      Provide a default value for the internationalization
                 variables that are unset or null. (See the Base
                 Definitions volume of POSIX.1‐2017, Section 8.2,
                 Internationalization Variables for the precedence of
                 internationalization variables used to determine the
                 values of locale categories.)

       LC_ALL    If set to a non-empty string value, override the values
                 of all the other internationalization variables.

       LC_CTYPE  Determine the locale for the interpretation of
                 sequences of bytes of text data as characters (for
                 example, single-byte as opposed to multi-byte
                 characters in arguments and input files).

                 Determine the locale that should be used to affect the
                 format and contents of diagnostic messages written to
                 standard error.

       NLSPATH   Determine the location of message catalogs for the
                 processing of LC_MESSAGES.



STDOUT         top

       When the -l option is used to list commands, the format of each
       command in the list shall be as follows:

           "%d\t%s\n", <line number>, <command>

       If both the -l and -n options are specified, the format of each
       command shall be:

           "\t%s\n", <command>

       If the <command> consists of more than one line, the lines after
       the first shall be displayed as:

           "\t%s\n", <continued-command>

STDERR         top

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES         top




EXIT STATUS         top

       The following exit values shall be returned:

        0    Successful completion of the listing.

       >0    An error occurred.

       Otherwise, the exit status shall be that of the commands executed
       by fc.



       The following sections are informative.


       Since editors sometimes use file descriptors as integral parts of
       their editing, redirecting their file descriptors as part of the
       fc command can produce unexpected results. For example, if vi is
       the FCEDIT editor, the command:

           fc -s | more

       does not work correctly on many systems.

       Users on windowing systems may want to have separate history
       files for each window by setting HISTFILE as follows:


EXAMPLES         top


RATIONALE         top

       This utility is based on the fc built-in of the KornShell.

       An early proposal specified the -e option as [-e editor [old= new
       ]], which is not historical practice. Historical practice in fc
       of either [-e editor] or [-e - [ old= new ]] is acceptable, but
       not both together. To clarify this, a new option -s was
       introduced replacing the [-e -].  This resolves the conflict and
       makes fc conform to the Utility Syntax Guidelines.

       HISTFILE  Some implementations of the KornShell check for the
                 superuser and do not create a history file unless
                 HISTFILE is set. This is done primarily to avoid
                 creating unlinked files in the root file system when
                 logging in during single-user mode.  HISTFILE must be
                 set for the superuser to have history.

       HISTSIZE  Needed to limit the size of history files. It is the
                 intent of the standard developers that when two shells
                 share the same history file, commands that are entered
                 in one shell shall be accessible by the other shell.
                 Because of the difficulties of synchronization over a
                 network, the exact nature of the interaction is

       The initialization process for the history file can be dependent
       on the system start-up files, in that they may contain commands
       that effectively preempt the settings the user has for HISTFILE
       and HISTSIZE.  For example, function definition commands are
       recorded in the history file. If the system administrator
       includes function definitions in some system start-up file called
       before the ENV file, the history file is initialized before the
       user can influence its characteristics. In some historical
       shells, the history file is initialized just after the ENV file
       has been processed. Because of these situations, the text
       requires the initialization process to be implementation-defined.

       Consideration was given to omitting the fc utility in favor of
       the command line editing feature in sh.  For example, in vi
       editing mode, typing "<ESC>v" is equivalent to:

           EDITOR=vi fc

       However, the fc utility allows the user the flexibility to edit
       multiple commands simultaneously (such as fc 10 20) and to use
       editors other than those supported by sh for command line

       In the KornShell, the alias r (``re-do'') is preset to fc -e -
       (equivalent to the POSIX fc -s).  This is probably an easier
       command name to remember than fc (``fix command''), but it does
       not meet the Utility Syntax Guidelines.  Renaming fc to hist or
       redo was considered, but since this description closely matches
       historical KornShell practice already, such a renaming was seen
       as gratuitous.  Users are free to create aliases whenever odd
       historical names such as fc, awk, cat, grep, or yacc are
       standardized by POSIX.

       Command numbers have no ordering effects; they are like serial
       numbers.  The -r option and -number operand address the sequence
       of command execution, regardless of serial numbers. So, for
       example, if the command number wrapped back to 1 at some
       arbitrary point, there would be no ambiguity associated with
       traversing the wrap point. For example, if the command history

           32766: echo 1
           32767: echo 2
           1: echo 3

       the number -2 refers to command 32767 because it is the second
       previous command, regardless of serial number.



SEE ALSO         top


       The Base Definitions volume of POSIX.1‐2017, Chapter 8,
       Environment Variables, Section 12.2, Utility Syntax Guidelines

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  In the event of any
       discrepancy between this version and the original IEEE and The
       Open Group Standard, the original IEEE and The Open Group
       Standard is the referee document. The original Standard can be
       obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page
       are most likely to have been introduced during the conversion of
       the source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group               2017                            FC(1P)

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